Gaymar Industries, Inc., the assignee of this application, is the assignee of U.S. Pat. No. 5,875,282 (hereinafter referred to as “the '282 patent”). The '282 patent is directed to an apparatus for warming blood and other fluids to a desired temperature prior to introduction into a patient. The blood and other fluids flow through a pathway contained by a bag. That pathway provides high flow performance and normally provides uniform, gradual and energy efficient blood warming. The bag has a pair of guide rails and a warming device has a pair of corresponding apertures that work in conjunction to ensure the bag is properly inserted into the warming device.
The warming device contains at least one, and normally a pair of opposed, identical heater elements, a receptive slot down the middle in a horizontal plane with the possibility of two guide slots, one on each side of the receptive-slot. The optional guide rails align the bag so it can be spaced and located precisely between the two heater elements. The pair of guide rails, integrated into the sides of the bag, is parallel to one another providing sufficient rigidity for easy insertion of the bag, and being sized to allow easy insertion in only the correct orientation. The blood warmer preferably incorporates a microprocessor for precise control of the electric current provided to the heater. Fluid temperature can be measured by contact of a RTD sensor with a thin dielectric surface layer in contact with the bag and located proximal to the fluid outlet and within the heater elements. By monitoring the temperature of the fluid at the outlet of the bag, the temperature controller can compute and provide a visual display of the fluid temperature. In one embodiment, the sensed output temperature is an input parameter to the controller of the heater elements. The device efficiently warms the fluid to about 37.5° C. for anticipated input to a human and, is simultaneously designed to prevent the fluid from exceeding 42° C.
The apparatus disclosed in the '282 patent is a very good fluid warming device but the applicants continue to try to improve it. One improvement is directed to making sure the heating elements are in constant contact with the cassette to ensure the fluid in the fluid path is uniformly heated to the desired temperature. Applicants are unaware of fluid warming apparatuses for fluids designed to enter a patient that are materially distinct from the apparatus disclosed in the '282 patent, except for the following invention.